This application is related to the following applications filed concurrently herewith by the same Applicants and assigned to the same Assignee: U.S. Pat. No. 7,946,582, Issued May 24, 2011 and U.S. Pat. No. 8,128,088, Issued Mar. 6, 2012. The complete disclosures of these co-pending applications are incorporated in their entirety herein by reference.
Embodiments herein generally relate to modular printing systems and, more particularly, to embodiments of a multi-sheet buffer module and a modular printing system incorporating such a multi-sheet buffer module.
Modularity in printing systems is known. For example, U.S. patent application Ser. No. 12/211,853 of Bober et al., filed on Sep. 17, 2008, and U.S. patent application Ser. No. 12/331,768 of Mandel et al., filed on Dec. 10, 2008 (both of which are assigned to Xerox Corporation of Norwalk, Conn., USA, and incorporated herein by reference in their entirety) disclose electrostatographic printing systems comprising multiple modules (i.e., discrete interchangeable units). Each module comprises one or more of the printing system's functional components (e.g., sheet feeders, printing engines, sheet inverters, sheet buffers, finishers, etc.) structurally self-contained within its own supporting frame and housing (i.e., cabinet).
Oftentimes multi-page documents contain both single color (i.e., monochrome) pages and multi-color pages. Since it is more cost and time efficient to print single color pages using a single color (i.e., monochrome) printing engine vice a multi-color printing engine, modular printing systems incorporating heterogeneous printing engine modules (e.g., a single color and multi-color printing engine modules) in a tightly integrated parallel printing (TIPP) architecture have been developed (e.g., see U.S. patent application Ser. No. 12/211,853 of Bober et al. and U.S. patent application Ser. No. 12/331,768 of Mandel et al., incorporated by reference above). Such modular printing systems can print multi-page documents, having single color and multi-color pages. To ensure that the various single color and multi-color pages are printed on print media sheets by the appropriate printing engine(s), a sorting process is performed. Once printed, the single color and multi-color pages are merged in order to output the finished document. However, timing of sheet output from the different print engines to ensure proper page merging (i.e., to ensure that pages are in the proper order) presents a problem for a number of reasons. For example, since multi-color print engines are typically more costly to run and since multi-page documents typically have significantly more text-only pages than multi-color pages, it is more cost efficient to print all or batches of multi-color pages together. This minimizes the number of on-off and warm-up cycles performed by the multi-color printing engine during a single print job, but results in multi-color pages being printed out of order and, particularly, early. Timing of sheet output is further made difficult as a result of duplex printing and mixed printing (i.e., when a single sheet requires printing by one side by a single color printing engine and on the opposite side by a multi-color printing engine).
In view of the foregoing, disclosed herein are embodiments of a multi-sheet buffer module and a modular printing system incorporating the multi-sheet buffer module. The buffer module has parallel first and second sheet transport paths that extend in opposite directions (i.e., transport sheets in opposite directions) across a support frame. Multiple parallel sheet buffer paths extend from the first sheet transport path to the second sheet transport path. In operation, a stream of sheets (e.g., unimaged sheets, sheets previously printed in simplex or duplex format by the first printing module, etc.) is received by the first sheet transport path from a first printing module (e.g., a color printing module) and fed through to a second printing module (e.g., a single color printing module). During this process, selected sheets are diverted from the stream into the sheet buffer paths and held. After processing by the second printing module (e.g., simplex or duplex printing), the stream of sheets is received by the second sheet transport path and fed through to the first printing module for further processing and/or for final output, for example, to a finishing module. During this process, the sheet buffer paths will feed the buffered sheets into the second sheet transport path such that they are inserted at the proper locations back into the stream of sheets. Such a multi-sheet buffer module provides a buffering function, as necessary, during the various printing processes (e.g., single color printing in simplex or duplex format, multi-color printing in simplex or duplex format, and mixed printing (i.e., one side single color, one side multi-color)) performed by the different printing modules and further provides a buffering function to ensure that sheets fully printed by the different printing modules are merged in the proper order prior to output.
Generally, embodiments of a multi-sheet buffer module as disclosed herein can comprise a support frame having a first side and a second side opposite the first side. A first sheet transport path can extend across the support frame for transporting sheets in a given direction from a first sheet input port on the first side to a first sheet output port on the second side. Additionally, a second sheet transport path, which is parallel to the first sheet transport path, can extend across the support frame for transporting sheets in the opposite direction from a second sheet input port on the second side to a second sheet output port on the first side. Finally, a plurality of sheet buffer paths can extend between the first and second sheet transport paths for transporting sheets from the first sheet transport path to the second sheet transport path and each of the sheet buffer paths can have a length sufficient to hold one or more print media sheets.
The multi-sheet buffer module, as described generally above, can be configured (as shown) for insertion between two stacked printing modules in a modular printing system. For example, in such an embodiment the support frame can have a bottom side and a top side opposite the bottom side. The first sheet transport path can extend essentially vertically across the support frame for transporting sheets in an upward direction from a first sheet input port on the bottom side of the support frame to a first sheet output port on the top side of the support frame. Additionally, a second sheet transport path, which is parallel to the first sheet transport path, can extend essentially vertically across the support frame for transporting sheets in a downward direction from a second sheet input port on the top side of the support frame to a second sheet output port on the bottom side of the support frame. Finally, a plurality of sheet buffer paths can extend essentially horizontally between the first and second sheet transport paths for transporting sheets from the first sheet transport path to the second sheet transport path.
During operation of the multi-sheet buffer module, the first sheet transport path can receive, at the first input port, a stream of sheets and can feed the stream of sheets out the first sheet output port. During this process, at least one sheet buffer path can divert at least one selected sheet from the stream and can hold that selected sheet. Subsequently, the second sheet transport path can receive, at the second input port, the stream of sheets and can feed the stream out the second sheet output port. During this process, any sheet buffer paths holding selected sheets can feed the selected sheets into the second sheet transport path such that they inserted back into the stream at predetermined points. To accomplish this, the buffer module can comprise a controller operatively connected to the first sheet transport path and the sheet buffer paths so as to control movement of sheets within the buffer module. Specifically, each sheet buffer path can have a corresponding gate adjacent to the first sheet transport path and one or more sheet transport devices. Each gate can be selectively controlled (e.g., by the controller) to force selected sheets to enter the sheet buffer paths on demand. Additionally, the sheet transport device(s) in each buffer path can be selectively controlled (e.g., by the controller) to force selected sheets, which are being held, to exit into the second sheet transport path on demand.
The above-described multi-sheet buffer module embodiments can be incorporated into a modular printing system with multiple printing modules in order to arrange sheets within a multi-page document in the proper order prior to output. The multi-sheet buffer module embodiments provide the additional advantage of allowing for sheet buffering during the various printing processes performed by the different printing modules. Specifically, such a modular printing system can comprise a first printing module (e.g., a multiple color printing module), and a second printing module (e.g., a single color printing module). The first printing module and the second printing module in this modular printing system can, for example, operate in tandem to print a multi-page document having single color sheets in simplex or duplex form, multiple color sheets in simplex or duplex form and, optionally, mixed sheets (i.e., sheets with single color printing one side and multi-color printing on the opposite side of the sheet). The multi-sheet buffer module, as described in detail above, can be positioned between the first printing module and the second printing module. For example, in the case of stacked printing modules, the buffer module can be positioned on top of the first printing module and below the second printing module. In this configuration, the multi-sheet buffer can provide any required sheet buffering during the various printing operations performed by the first and second printing modules and can also provide sheet buffering to arrange fully printed sheets within a multi-page document in the proper order prior to output.
During operation of the modular printing system, the first printing module (e.g., the color printing module) can receive unimaged sheets from, for example, a feeder module. Once in the first printing module, some of the sheets can be processed (i.e., can be printed in simplex and/or duplex form by the first printing module) and all sheets (i.e., any unimaged sheets and any printed sheets) can be forwarded in a stream to the buffer module. In the buffer module, the first sheet transport path can receive the stream of sheets at the first input port from the first printing module and can begin feeding this stream of sheets out the first sheet output port into the second printing module (e.g., into the single color printing module). During this process, at least one sheet buffer path can divert at least one selected sheet from the stream and can hold that selected sheet such that the sheet is not passed into the second printing module for processing. Once in the second printing module, the remaining sheets in the stream can be processed (i.e., can be printed in simplex and/or duplex form by the second printing module). Subsequently, the second sheet transport path can receive the stream of sheets at the second input port from the second printing module, as processed by the second printing module, and can begin feeding the stream out the second sheet output port back into the first printing module. During this process, any sheet buffer paths holding selected sheets (i.e., buffered sheets) can feed the selected sheets into the second sheet transport path such that they are inserted back into the stream at a predetermined point. Once back in the first printing module, individual sheets within the stream may be further processed by the first printing module, transported back into the buffering module for further processing as described above and/or finally output, for example, to a finishing module.
These and other features are described in, or are apparent from, the following detailed description.